/Engine/Source/Runtime/Core/Public/Math/UnrealMathUtility.h
Computes the barycentric coordinates for a given point on a tetrahedron (3D)
Vector containing the four weights a,b,c,d such that Point = a*A + b*B + c*C + d*D
static FVector4 ComputeBaryCentric3D ( const FVector & Point, const FVector & A, const FVector & B, const FVector & C, const FVector & D )